The invention relates to systems and methods for replacing, repositioning and repairing a section of subsea pipe located on a seabed, such as pipe used in an oil and gas transportation pipeline.
Known methods for repairing subsea oil and gas transportation pipelines located on soft and sloping seabed conditions require specialized pipeline repair equipment and procedures, and/or terrain modifications to improve the stability. Currently used methods for pipe repair on slopes of 5 to 10° with respect to the horizontal generally require minor terrain modifications. Pipe repair on slopes of greater than 10° generally require some equipment modifications. For instance, load handling equipment used for such repairs must be stabilized with a stable anchoring system such as a large cumbersome mud mat system, such as, for example, the system disclosed in U.S. Pat. No. 6,290,431. Such systems cannot be stabilized for use in sloping terrain without additional anchoring, making them impractical on sloping or uneven terrain. On steep slopes of greater than 15°, mud mat systems have been found to be unstable.
It would be desirable to have systems and methods to accommodate subsea pipeline repairs on seabed conditions ranging from very soft and powdery soil to moderate clay and on topography ranging from relatively flat to inclines and declines of up to about 30° with respect to the horizontal.